Dystonia is a disorder characterized by involuntary muscle contractions that cause slow repetitive movements or abnormal postures. The movements may be painful, and some individuals with dystonia may have a tremor or other neurologic features. There are several different forms of dystonia that may affect only one muscle, groups of muscles, or muscles throughout the body. Some forms of dystonia are genetic but the cause for the majority of cases is not known.
Symptoms of Dystonia
Dystonia can affect many different parts of the body, and the symptoms are different depending upon the form of dystonia.
Symptoms may include:
- Foot cramp or dragging
- Worsening in handwriting after writing several lines
- Involuntary movements in the neck, including a turn or pull
- Rapid blinking or spasms in both eyes
- Difficulty speaking
In some cases, dystonia can affect only one specific action, while allowing others to occur unimpeded. The initial symptoms can be very mild and may be noticeable only after prolonged exertion, stress or fatigue. Over a period of time, the symptoms may become more noticeable or widespread; sometimes, however, there is little or no progression.
Causes of Dystonia
The cause of dystonia is not known. Researchers believe that dystonia results from an abnormality in or damage to the basal ganglia or other brain regions that control movement. There may be abnormalities in the brain’s ability to process a group of chemicals called neurotransmitters that help cells in the brain communicate with each other. There also may be abnormalities in the way the brain processes information and generates commands to move. In most cases, no abnormalities are visible using magnetic resonance imaging or other diagnostic imaging.
When Do Symptoms of Dystonia Occur?
Dystonia can occur at any age, but is often described as either early, or childhood, onset versus adult onset.
- Early-onset dystonia often begins with symptoms in the limbs and may progress to involve other regions. Some symptoms tend to occur after periods of exertion and/or fluctuate over the course of the day.
- Adult-onset dystonia usually is located in one or adjacent parts of the body, most often involving the neck and/or facial muscles. Acquired dystonia can affect other regions of the body.
Dystonias often progress through various stages. Initially, dystonic movements may be intermittent and appear only during voluntary movements or stress. Later, individuals may show dystonic postures and movements while walking and ultimately even while they are relaxed. Dystonia can be associated with fixed postures and shortening of tendons.